Real-time tool condition monitoring using wavelet transforms and fuzzy techniques

Wavelet transforms and fuzzy techniques are used to monitor tool breakage and wear conditions in real time according to the measured spindle and feed motor currents, respectively. First, continuous and discrete wavelet transforms are used to decompose the spindle and feed ac servo motor current signals to extract signal features so as to detect the breakage of drills successfully. Next, the models of the relationships between the current signals and the cutting parameters are established under different tool wear states. Subsequently, fuzzy classification methods are used to detect tool wear states based on the above models. Finally, the two methods above are integrated to establish an intelligent tool condition monitoring system for drilling operations. The monitoring system can detect tool breakage and tool wear conditions using very simple current sensors. Experimental results show that the proposed system can reliably detect tool conditions in drilling operations in real time and is viable for industrial applications.     

Persistent photoconductivity as a tool for monitoring oxide cluster concentration in silicon wafers

Many semiconductor devices rely on the so-called “denuded zone” of the silicon wafers. It is therefore essential to have a simple means to monitor the purity of this zone. It will be shown that persistent photoconductivity (PPC) can be related to the oxygen concentration in the wafer, and thus can be used to evaluate the quality of the denuded zone. A test structure was designed and the PPC measurements performed. They clearly indicate that the intensity of the PPC effect is roughly proportional to the amount of oxygen clusters in the wafer.     

Intellectual capital analysis as a strategic tool

This publication contains reprint articles for which IEEE does not hold copyright. The full-text attachment does not include this article. However, you may purchase the article from the Ask*IEEE Document Delivery Service at http://www.ieee.org/services/askieee/     

Fast wafer level reliability monitoring as a tool to achieve automotive quality for a wafer process

This work describes and discusses fast wafer level reliability (fWLR) Monitoring as a supporting procedure on productive wafers to achieve stringent quality requirements of automotive, medical and/or aviation applications. Examples are given for the various reliability topics: dielectrics, devices, metallisation, plasma charging with respect to required test structures, stress methods and data analysis. Application areas of fWLR are highlighted and limitations considered. Further aspects such as relevant reliability parameters, sampling strategies and out of control action plans are discussed.     

Aging signature properties and an efficient signature determination tool for online monitoring

Increased reliability problems in deep sub-micron CMOS technologies have led to a dramatic decrease of lifetime of analog integrated circuits. To palliate this problem, several reliability-aware design approaches have been developed. Reconfigurable circuit design is one of those approaches, which is based on reconfiguring the circuit considering degradation in circuit performances. Sense & React (S & R) approach is the well-known reconfigurable design approach, where degradation in circuit performances are sensed and a pre-established recovery operation is applied to heal the circuit. In practice, indirect measurements are preferred during sense operation, in which electrical quantities are measured in order to determine time to recovery. Determination of the time to recover is the most critical part of a S & R system. One or more circuit variables are selected out of all measurable circuit quantities. The selected signature should have some attributes to be used as the aging signature to reduce the measurement cost. However, efficient aging signature properties have not been defined in the literature yet. Moreover, the designer determines the aging signature manually by performing an iterative search and evaluation on aging simulation results, and there is no tool to ease this time consuming process. This paper clearly describes the aging signature properties and proposes an automatic signature selection tool that determines the most efficient signature for sense operation.     

太阳能电池发电量实时监控系统

为了实时监控太阳能电池发电量,设计一种太阳能电池发电量实时监控系统,该系统利用单片机和霍尔电流传感器实时测量太阳能电池的输出电压、电流得到输出功率,然后经运算得到电量值送液晶显示器显示结果.实验表明:该系统测量误差小于3%,且低成本、低功耗.使其在离网光伏系统中应用广泛.     

太阳能电池发电量实时监控系统

为了实时监控太阳能电池发电量,设计一种太阳能电池发电量实时监控系统,该系统利用单片机和霍尔电流传感器实时测量太阳能电池的输出电压、电流得到输出功率,然后经运算得到电量值送液晶显示器显示结果。实验表明：该系统测量误差小于3％．且低成本、低功耗,使其在离网光伏系统中应用广泛。     

Laser THz emission microscope as a novel tool for LSI failure analysis

We have proposed and developed a novel technique for a non-contact inspection of defective interconnections in an LSI chip using a laser terahertz emission microscope (LTEM). The LTEM measures the THz emission images of an LSI chip by scanning it with fs laser pulses. When a fs laser pulse irradiates a p–n junction in an LSI chip, transient photocurrent flows into interconnections resulting in the emission of the THz pulse into free space. We investigated the characteristics of the THz emissions from simple test element group samples which consist of p–n junctions connected to metal lines. It was found that the metallic lines connected to photo-excited p–n junctions worked as THz emission antennae which enhance the emission efficiency of THz pulses near their resonant frequencies corresponding to the line lengths. This result indicates that THz emission signals from p–n junctions in circuits strongly depend on the structure of the interconnections. We show the successful results on the inspection of defective interconnections in MOSFET devices and C7552 ISCAS’85 benchmark circuits using LTEM. By comparing the THz emission images between a normal circuit and a defective one, it is possible to identify the p–n junctions connected to the defective interconnections without electrical contacts.     

Light emission as an analysis tool for GaAs ICs

As GaAs IC integration continues, device characterization and failure analysis get more difficult to perform. Standard visual and electrical inspections are becoming less adequate to evaluate devices and determine root cause of failures. A relatively new technique, used for several years on silicon devices, is light emission microscopy. The properties of light emission on silicon devices have been known for several decades. The light-producing properties of GaAs, a direct bandgap material, make it a natural for light emission study. This overview is intended to discuss the methodology and results of GaAs MESFET light emission.     

光纤传输网实时监测系统

随着光纤网络的迅猛发展,光网络的维护和管理面临巨大的挑战,为此设计光纤传输网实时监测系统.该系统基于先进光器件、光信号处理技术、网络技术和OTDR技术实现对光纤传输网的自动实时监测,实现了光纤中断故障的自动精确定位.     

Real-time signal processing for fetal heart rate monitoring

An algorithm based on digital filtering, adaptive thresholding, statistical properties in the time domain, and differencing of local maxima and minima has been developed for the simultaneous measurement of the fetal and maternal heart rates from the maternal abdominal electrocardiogram during pregnancy and labor for ambulatory monitoring. A microcontroller-based system has been used to implement the algorithm in real-time. A Doppler ultrasound fetal monitor was used for statistical comparison on five volunteers with low risk pregnancies, between 35 and 40 weeks of gestation. Results showed an average percent root mean square difference of 5.32% and linear correlation coefficient from 0.84 to 0.93. The fetal heart rate curves remained inside a +/- 5-beats-per-minute limit relative to the reference ultrasound method for 84.1% of the time.     

Silicon micromachined diamond-shaped AFM cantilever for accurate mechanical tests of MEMS structures

A novel single crystalline silicon diamond-shaped atomic force microscope (AFM) cantilever for accurate mechanical tests of MEMS structures is presented. A strip bending test of micromachined gold thin film strip specimens has been performed using the proposed AFM cantilever. The experimental results show that a more accurate and uniform bending test is possible with this new cantilever by suppressing lateral motions of a conventional beam-shaped cantilever.     

Real-time application to multiprocessor-system-on-chip mapping strategy for system-level design tool

A new static mapping technique is presented that can be integrated in a system-level design tool for modelling and simulating real-time applications onto an embedded multiprocessor system. The results of preliminary experiments indicate that the proposed two-phase mapping approach can achieve a good trade-off between the efficiency in resource usage and processor load balancing, as well as the minimisation of the inter-processor communication cost.     

A statistical mechanical analysis of postural sway using non-Gaussian FARIMA stochastic models

In this paper, postural sway is modeled using a fractional autoregressive integrated moving average (FARIMA) family of models: the center-of-pressure (COP) motion is viewed in terms of a self-similar, anti-persistent random-walk process, obtained by fractionally summating non-Gaussian random variables, whose correlation structure for small time lags is shaped by a linear time-invariant low-pass filter. The model parameters are: the strength of the stochastic driving, e.g., the root mean square (rms) value of the time-difference COP motion; the DC gain, damping ratio and natural frequency of the filter; the Hurst exponent, which measures the random-walk antipersistence magnitude. In the proposed modeling procedure, a graphical estimator for determining the Hurst exponent is cascaded to a method for matching autoregressive (AR) models to fractionally difference COP motion via higher order cumulants. The effect of the presence or absence of vision on the model parameter values is discussed with regard to data from experiments on healthy young adults.     

An analysis of ternary simulation as a tool for race detection in digital MOS circuits

Recently, Bryant developed a new switch level model for the functional simulation of race-free digital MOS circuits. The model establishes a formal correspondence to classical circuit theory. Thus the correctness of any simulation algorithm w.r.t. this model is a strong justification for using the algorithm. In [4,12] correct and efficient algorithms have been reported for simulating circuits that do not have internal race conditions. In [1] Bryant suggests to use ‘ternary’ simulation for detecting race conditions in MOS circuits. He justifies his simulation method with a couple of example circuits; however, he does not extend the simulation model to cover circuits that have internal races.In this paper we develop a general framework for simulating MOS circuits that may have race conditions. We use this framework to prove Bryant's conjecture in a suitable extension of his simulation model. We give efficient simulation algorithms for the model and remark on its limitations.     

Videoconferencing as a communication tool

With videoconferencing available on the desktop, the technology is becoming feasible for small- to medium-sized companies, as well as mobile workers. Videoconferencing applications range from internal company communications, educating and training remote employees, to telecommuting. It can even eliminate certain travel requirements, thereby cutting costs. In spite of several factors which are fueling the growth in videoconferencing, early projections have been overly optimistic. A literature review reveals that many technological and other barriers are preventing videoconferencing from gaining mainstream popularity. Users are primarily concerned with the costs of hardware and usage, interoperability, and poor quality. Advancements in compression algorithms and chip speed have made videoconferencing affordable to more people in the last decade. However, a video signal with quality acceptable only to some is still very costly and relatively complicated to utilize with the transport capabilities of today. Some say the turning point will not occur until hardware prices drop enough for video to become an add-on to users' PCs     

Ray tracing as a design tool for radio networks

Efficient radio ray tracing programs developed particularly for reflector-rich environments are described. These image-based, dual-grid, scalar, coherent, ray tracing programs generate maps, (two-dimensional slices) of three-dimensional standing wave patterns for continuous wave illumination. The calculated maps are used to estimate system coverage quality in a macroscopic sense and to investigate design alternatives regarding antenna beamwidths, boresight orientations, spatially averaged signal strengths, and so forth. The programs run fast enough on engineering workstation to support indoor radio system design, but not fast enough for interactive use. Examples are given to illustrate the use of the programs     

Modulation spectroscopy as a tool for electronic material characterization

Modulation spectroscopy is an optical characterization tool that can be of great utility to the materials scientist. We present here numerous examples where a simple photo-reflectance and electroreflectance setup is used in our laboratory to determine such important material parameters as alloy composition and carrier concentration in a very short time. For determining alloy composition in semiconductors, contactless room temperature photoreflectance is nearly as sensitive as low temperature photoluminescence. Examples will be given on how to determine: the effects of surface preparation and implant damage; alloy composition and carrier homogeneity for large area wafers to better than 1%; the segregation coefficient of isoelectronic impurities in bulk semiconductors; the sub-band energies in quantum well structures; and the presence and homogeneity of built-in electric fields in MODFET structures. Particular emphasis will be placed on band edge and exciton effects on the photoreflectance and on the criteria used to distinguish between them. Materials studied included Si doped GaAs, Al_xGa_1-xAs for variousx grown by OMVPE and MBE, bulk InP doped with iso-electronic As and Sb, and MODFET structures.     

RELVEC — a tool for control system reliability analysis

This article will present a computerized reliability analysis tool for large control systems. It will also show a new dynamic representation of system structure. It enables us to model the physical system only once for any number of control tasks. The algorithm for computing minimal cut sets for the control tasks has been developed and automated. The result is RELVEC, an interactive computer program that performs reliability/availability calculation, sensitivity analysis and critical component identification. It can handle two repair policies and common mode failures. Reconfiquring of the physical system or the control tasks is simple. RELVEC is becoming an everyday tool in control system reliability analysis at VTT.